Magnetic record transducing apparatus having a backing element for coupling a recordtape to the magnetic head



Dec. 26, 1950 A. P. DANK MAGNETIC RECORD TRANSDUCING APPARATUS HAVING ABACKING ELEMENT FOR COUPLING A. RECORD TAPE TO THE MAGNETIC HEAD 6Sheets-Sheet 1 Filed Aug. 16, 1946 74 I: FEM

##EE REC.

572 73 FW. FE

INVENTOR A. P DANK 3 Y E N R O T T A Dec. 26, 1950 A. P. DANK 2,535,486

1 MAGNETIC RECORD TRANSDUCING APPARATUS HAVING A BACKING ELEMENT FORCOUPLING A RECORD TAPE TO THE MAGNETIC HEAD 6 Sheets-Sheet 2 Filed Aug.16, 1946 III! LILEL IN VEN TOR. APDANK PAM A T7'ORNEXS Dec. 26, 1950 A PDANK 2,535,486

MAGNETIC RECORD TRANSDUCING APPARATUS HAVING A BACKING ELEMENT FORCOUPLING A RECORD TAPE TO THE MAGNETIC HEAD v 6 Sheets-Sheet 3 FiledAug. 16, 1946 INVENTOR.

%EQANK ATTORNEYS Dec. 26, 1950 2,535,486

A.'P. DANK MAGNETIC RECORD TRANSDUCING APPARATUS HAVING A BACKINGELEMENT FOR COUPLING A RECORD TAPE TO THE MAGNETIC HEAD 6 Sheets-Sheet 4Filed Aug. 16, 1946 INVENTOR AP DANK ATTORNEYS Dec. 26, 1950 A. P. DANK2,535,486

MAGNETIC RECORD TRANSDUCING APPARATUS HAVING A BACKING ELEMENT FORCOUPLING A RECORD TAPE TO THE MAGNETIC HEAD 6 Sheets-Sheet 5 Filed Aug.16, 1946 S t. l

INVENTOR. A. P. DANK Q *9 g R 41,!

M A law.

ATTORN EYS Dec. 26, 1950 A. P. DANK 2,535,486

' MAGNETIC RECORD TRANSDUCING APPARATUS HAVING A BACKING ELEMENT FORCOUPLING A RECORD TAPE TO THE MAGNETIC HEAD Filed Aug. 16, 1946 I 6Sheets-Sheet 6 INVENTOR AP DANK /40W 4 W ATTORNEYS Patented Dec. 26,1950 MAGNETIC RECORD TRANSDUCING APPA- RATUS HAVING A BACKING ELEMENTFOR COUPLING A RECORD TAPE TO THE MAGNETIC HEAD Alfred P. Dank, Euclid,Ohio, assignor to The Brush Development Company, Cleveland, Ohio, acorporation of Ohio Application August 16, 1946, Serial No. 690,878

3%) Claims.

This invention relates to magnetic recording and reproducing apparatuand more particularly to such apparatus utilizingas a magnetic recordingmedium a thin flexible magnet'c record memb :r or track, such as a tapeor filament which may be stored on reels, although in some of itsaspects the invention is not limited to sich recording medium.

Among the objects of the invent'on are no el magnetic recording devicesof the foregoing type embodyingvarious features which make themfoolproof and simple i operationan'iwhrh eliminate difficultiesheretofore encountered with such devices.

The foregoing and other objects of the iir'ention will be bestunderstood from the follov'ing description of exemplifications thereof,reference being had to the accompanying drawings where- Fig. 1 is asimplified diagrammatic view illustrating the general relationship ofthe mechanical and electric elements of a mechanically simple form ofmagnetic recording and reproducing apparatus exemplifying the invention;

Fig. 2 is a simplified circuit diagram of the elements of the reversibledrive and of the drive control of the magnetic recording and reproducingdevice of Fig. 1;

Fig. 3 is a top view of a recording apparatus according to theinvention;

Fig. 4 is a cross-section of the apparatus of Fig. 3 along the brokenline 4-4.

Fig. 5 is a top view of a portion of a magnetic head assembly that maybe used in the recording apparatus of the invention;

Fig. 6 is a side view of the magnetic head assembly portion of Fig. 5;

Fig. 7 is a front view of the magnetic head assembly portion of Fig. 5;

Fig. 8 is a top view similar to that of Fi 3 of another form ofrecording apparatus according to the invention;

Fig. 9 is a partly sectional view of the capstan structure of Fig. 3;

Fig. 10 is a top view simi ar to Fig. 3 of a further modified apparatusof the invention;

Fig. 11 is a diagrammatic representation of one modification ofimpelling means according to the invention, for use with a magnetictransducing apparatus; and

Fig. 12 is afragmentary view of an arresting device which is used inanother form of the invention.

In the copending applications of Otto Kornei, Serial No. 685,092, filedJuly 20, 1946, and Serial No. 685,093, filed July 20, 1946 (the latterapplication has been abandoned). there is described a novel magneticrecording and reproducing system and method uti'iiing as a magneticrecord- Eng a stratum of bonding compound having substantially uniformlydispersed th rein permanently magnetizable powder particles and forminga th'n flexible tapeor filament-like magnetic record track andcooperating with a magnetic record transducer head, the pole faces ofwhich are align'd along one side of the surface of the stratum and caable of recording magnetic signals with a signal-to-noise ratio of theorder of about 50 db., while the recording medium moves only at arelatively very low speed, such as eight inches per second.

The magnetic recording apparatus of the present invention provides anovel reeling mechanism for such recording system which makes itpossible to produce high quality magnetic records on such thin,flexible, although mechanically weak, magnetic recording media with arelatively high degree of fidelity, while assuring that the mechanicalforces to which the thin, flexible and relatively-weak magneticrecording media are subjected during the reeling operation, are at alltimes kept so low as to practically eliminate breakage of the recordingmedium not only when it is reeled at a slow speed during a recording orplayback operation, but also while it is reeled at an extremely highspeed during a rewinding operation or when it is desired to reel it inforward direction at a high speed.

Figs. 1 and 2 ilustrate in a smplified diagrammatic manner the generalrelationship of the mechanical, magnetic and electric elements of amechanically-simple form of a magnetic recording and reproducingapparatus of the invention designed specifically i'or use in connectionwith a recording medium formed of a thin limp elongated record member,such as a tape made of paper or a plastic or synthetic resin compound,provided at least one exposed surface with a layer of permanentlymagnetizable powder dispersed in a bonding compound forming part of therecording medium.

However, various features of the invention disclosed herein areapplicable to other magnetic recording media, such as in the form ofthin filaments, of fibre or filament forming linear polymers, or threadsof silk, embodying or coated with a layer of inagnetizable particles.Some of the features of the invention are also applicable to magneticrecording media formed of metallic term-magnetic tapes, filaments and.wires.

stag-4st In Figs. 1 and 2 the magnetic recording medium is indicated bydash-doubl -dot line 3!, and is arranged to be reeled from supply reel32 onto take-up reel 33. The supply reel 32 and the take-up I181 33 aremounted on reel shafts 6i andiifi, respectively, which are driven by,reel drive mechanism so that during the recording and the playbackprocess the recording medium 3! is impelled in the direction of thearrow 3l-F, and reeled from supply reel 32 ont.0 ihe take-up reel 33. Inorder to play backthe re? corded program or to make a new record on therecording medium, it must be rewound or reeled from take-u reel 33 ontosupply reel=3-2.

To simplify the description of the featuresof the invention, a slowspeed reeling operation in the direction of the arrow '3fl-rF; duringwhich a new record is made on the recording medium or a previously maderecord is played back, will be designated a forward reeling operation,reel 32 will be designated the supply reel and reel .33, the take-upreel. In addition, the fast rewind- -ing operation during which therecording medium .is reeled back from the takeup reel 33 on the supplyreel 32 will be designated as the rewind operation, and a fast reelingoperation in .the forward direction indicated by the arrow (ii-F, inorder to quickly reach a desired point on the recording medium forplaying back a-recrd sequence made thereon or for replacing it withanother record sequence, will be designated as the fast forward reelingoperation.

In the particular form of recording apparatus shown, the take-up reel isdriven in counterclockwise direction during a forward reeling operation,and the supply reel 32 is similarly driven in counter-clockwisedirection as indig ted by the arrow during the rewinding operat on. Thereels 32, 33 are similar to those used for standard amateur-type motionpicture reels. Thus, in the case of a recording medium formed of a thintape one-quarter of an inch wide, each reel may be made with an innerreel core 1% inches in diameter so that a reel seven inches in diameteris sufiigient for storing a length of the recording medium required tomake a record of oneehalf hour duration.

During the recording or playback process the recording medium 35 isguided from the supply reel 32 past a record transducer head structure36 along a forward drive path indicated by arrow (ii-F, so as tocouplingly engage the periphery of a capstan-like roller 3'1 and passtherefrom along the guide surface of a forward limit control member 38to the take-up reel 33. During the rewinding process, the recordingmedium 3! may be guided along the same path just described, as it isreeled from the take-up reel 33 onto the supply reel 32. However, it issimpler to remove the record tape 3! from the capstan roller and carryon the rewinding process by guiding the tape 3! directly back from thetake-up reel 33 onto the supply reel 32, along the fast reeling orrewind path indicated by the dash-triple-dot line 3 l-R, the tape beingguided along the guide surface of a rewind limit control element 38.This fast reeling path 3l--R may also be utilized whenever it isdes'..ed to reel the record member fast in forward direction on thetakeeup reel, for instance, in order to quickly reach a desired portionofa long record.

The two limit control members 33, 39 are combined with limit switches33-FL, 39-.RL which are actuated from the non-operated position .25,i950. Th5: transducer head structure shown has an erasing head 4| and arecord .transducing headAZ each provided with windshown to an operatedposition when the respective limit control member 38, 39 is operated bythe recording medium 3|.

The magnetic head structure 36 is not part of thelpresent invention andmaybe of the type described in the .oopending .application of OttoKornei, Serial No. 688,034, filed August 2, 1946, Ratent No. 2,523,576,which issued on September 33 loss and a mag-netic core structure whichhas pole pieces separated by a non-magnetic gap along'which therecordingmedium is moving in the direction of "the arrow 3|F during a magneticrecording or playback process.

During the magnetic recording process, each element of the recordingmedium 3! passes successively first past the gap region of the erasinghead 4! and then past .the gap region of the re- .cording'head '42. Therecording system shown in Fig. l .is arranged to carry on magneticrecording and reproducing operations under the control of a =multi-b1aderecording switch 43 which controls the electric circuit connections ofthe recording head structure with the amplifier and signal pickup andreproducingdevices of the system, additional control means, generallydesignated T0,.serving toprovide for the p-roperoperationof the drivingmechanism during the recording, playback and other reeling operations.

The recording switch 43 is a standard multiblade switch shown operatedmanually by a knob between the full-line right-hand playback positionshown and the left-hand dotted-line recording position 431-1. The drivecontrol unit it? is indicated in Fig. l diagrammatically .as aconventional push button iype Selector control arrangement provided witha series of button-operated push rods TI, 12, 13, M, i5, i3, also designated by the legends STRT for start, FW for forward, for fast forward,REW for rewind,

STP fo s op. and REC fo re In such conventional push-rod selector con-.trol ,rnechan-ism, a slidably mounted latch bar H, which 'is biased toa latching position as by a. sprin ll-l, is arranged to retain in an in-Ward operative position one or more of the previously actuated pushrods,such as push rod 15 shown latched in the inward position, the latch bar[1 being actuated to release the latched push rod Whenever it isactuated in lateral direction a inst the biasing action of spring iii bya cam surface of a latch projection 78 shown provided on the push rods12 to 1.6 which are to be latched when selectively actuated to an inwardposition.

The latch bar and the mounting structure elements IO-l, '|02 of the,push-rod mechanism are provided with suitable slits through which theseveral push rods are arranged to be slidably movable between the inwardoperative position and the released outward position to which actuate,its switch to. the operated position.

It will be noted that the push rod H of the starting switch rod is. notprovided with a latch prqiection. 1.8. so that when .it..is actuated tothe and |4-D which are arranged so that whenever the respective pushrods l2, 14 are actuated to the inward operated position, the respectivelevers '|2-D, '|'4D are actuated from the nonoperated position shown toan operated position for performing a desired mechanical controloperation, as explained hereinafter. Although the push-rod selectorcontrol arrangement is shown in Fig. 1 for controlling the operation ofthe switches and mechanical control elements of the reeling mechanism,other types of analogous control arrangements may be used, for instance,a rotary type selector control arrangement movable to a plurality ofdifferent angular positions and provided with cam elements forselectively actuating the different switches and the differentmechanical control elements in the different settings of the rotarycontrol member.

With the control arrangement of Fig. 1 as shown, a record recorded onthe recording medium 3| will be played back when the main recordingswitch 43 is in the full-line position shown while the recording track3| is reeled on the take-up reel 33. In such play-back condition, therecording switch 43 establishes the following playback circuits:

Contacts and 2 of the recording switch 43 connect the lead from thewindings of the recording head 42 which now operates as a playback headto the input side of a pre-amplifier 44, the output of which isimpressed on an additional playback amplifier 45, the output side ofwhich is connected through switch blade 3 of the recording switch 43 inits playback position to the reproducing device shown in the form of aloudspeaker 46.

In order to make a new record on a portion of the moving recordingmedium 3| when the switches l2--C and '|6-C are operated by thepush-button rods 12, 16 in the manner explained hereinafter, therecording switch 43 has to be thrown to the left-hand dotted-lineposition 43-| in which it establishes in connection with the otheroperated switches of the device the following recording circuit:

Contact blade 4 of the recording switch 43 in its left-hand position, inconjunction with contact |C of push rod switch |5-C, connects a sourceof high frequency oscillations, such as an oscillator 41 to a source ofpositive electric power supply indicated by (B+). The oscillator circuitas well as the other analogous circuits described hereinafter, are showncompleted by conventionally indicated ground connections to which arealso connected the negative terminals of all D. C. supply sources. Highfrequency oscillator 41 is shown connected directly to the windings ofthe erasing head 4|, the energizing circuit of which is completed bycontacts |C of the forward limit switch 38-FL when it is held in theoperated condition by the moving recording medium, in the mannerexplained hereinafter.

The high frequency erasing current supplied by the oscillator 41 to thewindings of the erasing head 4| is of sufficiently large amplitude sothat each element of the thin magnetic recording medium 3| passing thegap region of the erasing head 4| is subjected to an alternating fiuxstrong enough to erase any previous magnetic signal records impressed onthe moving magnetic recording medium 3| and restore the magneticelements thereof to a magnetically neutral condition.

After being subjected to the magnetic erasing action by the erasinghead, each element of the moving recording medium 3|, upon reaching thegap region of the recording head 42, is subjected to the combined actionof a magnetic recording flux produced by the amplified signal currentsthat are to be recorded and the superposed high frequency biasing fiuxcomponent. In Fig. l, a conventionally shown microphone 48 serves as asource of signals which are to be recorded, and blade I of the recordingswitch 43 in its left-hand recording position connects the microphone 48to the input side of the pre-amplifier 44, the output of which isimpressed on an additional recording amplifier stage 49, the output ofwhich is supplied to the windings of the recording head 42 by a circuitincluding the operated contacts 20 of the push rod switch '|6C and thecontacts of the contact blade 2 of the recording switch 43 in theleft-hand recording position, the circuit being completed by the groundconnections shown.

The high frequency bias component of the recording flux is produced inthe recording head 42 by a high frequency current component derived fromthe oscillator 41 through an adjustable coupling condenser 49|, the highfrequency component of the current being mixed with the amplified outputof the recording amplifier 43 and supplied to the windings of therecording head 42 through the previously described circuit connection.Coupling condenser 49| and the other circuit elements of the system aredesigned and adjusted to mix a suitable component of the high frequencyoscillations produced by the oscillator 41 with the amplified signalcurrent supplied by the signal source, such as microphone 48 in suchmanner as to produce in the non-magnetic gap region of the recordinghead 42 the desired combination of signal recording flux and thesuperposed high frequency biasing flux component.

In general, when recording signals of the audible frequency range, goodresults are obtained by using a high frequency biasing flux of about 25to 30 kilocycles per second, and the same source of high-frequencyoscillations may be used in supplying the relatively largehigh-frequency erasing current to the erasing head 4|, as well as therelatively small high-frequency biasing component to the recording head42.

As indicated in Figs. 1 and 2, the additional amplifier 49 may bearranged to be supplied with its anode potential through the samecircuit which supplies the positive B potential to the oscillator 41, sothat the recording amplifier 49 is rendered operative only when therecording switch 43 is in the left-hand recording position.

According to the invention, the driving elements which impart drivingforces to the recording medium 3| and cause it to be reeled from onereel to the other are interconnected to the elements which impel thereels by yieldable coupling means which subject the thin flexiblereeject-Ase 7 cording-'mediumat all times only to very limitedforces-just sufficient -to-take up its'slacs, but-insuflicienttomaintain stable contact conditions between-the pole faces of therecording and erasing heads 42', 4| and the elements of the recordingmedium moving past it. In accordance with theinvention, the yieldablecoupling means may be for-med either by a magnetic flux fluid drive orbyother fiuid drives which are similar iii-their driving action to thatexerted by a magnet on a sheet-of metal, suchas copper, inwhich themagneti-nduces a current when-they move relatively to each other. Thismethod of driving has not only properties of smoothness andadjustability, Iout also provides a damping action which suppressesforces tending to impart flutter to the portion of the recording mediumwhich is-im'- pelle'di past the record transducing head.

Fig. 1 indicates diagrammatically one simple form of a drivingarrangement based on the principlesvof the invention; Duringtherecording or'playback operation or during the normal forward reelingoperation, the recording medium 31 isimpelled at a constant speed pastthe two heads 41, 42 through its engagement with the capstan roller 31forming'part of constant speed impelling means. The constant speedimpelling" means include an electric motor 5! having ashaft 52 whichiscoupled through arubbertired floating coupling pulley 53 tothe rim ofa fly-wheel member 54 to whiclithe constant speed impelling roller orcapstan 37 isconnected, the capstan roller 31 andthe flywheel 54 havinga common-shaft 55serving as their revolving support.

In: order to prevent the recording medium, suchas-the-tape or filament31-; withdrawn from the supply reel 32' from becoming'slack', and inorder to. assure-that -it moves at all times under a small'limitedforce, a shaft Si onwhichthe supply reel'32-is'mounted is subjected toalimited bralsing action exerted, forinstance, by abraking. pad 62supported bya resilient brake-- arm 6-2"l and engaging the surface of acollar or disc 53 affixed to the shaft 6-! andwhich'is shown servingas-th'ecoupling seaton which the supply reel- 32' is seated.

Inthe specific drive arrangement shown, the shaft 8 forms-a revolvingpartof an" electric motor Edi suitably supported onthe-frande structureof-' the reeling mechanism underneath a mounting panel so as to exposethrough-a hole in'=the' topof the panel the seating member 83 of theshaft. The seatingrhember-or collar 83 affixed'to the shaft just belowits upwardly'pro jecting end'maybe providedwith an upwardly projectingcoupling or'key'pin 62 arranged to inter-fit witha-couplingnotchextending from the central hole formedon the hub of "eachreel 32; 33 so as to-establisha coupling connection between the shaft 6iand a reel, such as reel-3'2, seated-on the seating collar 83.Alternatively, each reel support shaftmay be pro ided with atransversely extending key arranged to interfit with coupling notchesextending" from the central hole formed 'in th'e hub of the reel.

l'n' one'commercial form of a recordingmechanism-of' the type shown inFig. 1, each of the reels $2, 33 are designed to revol e around avertic-all axis; With such reel arrangement, the two reels may-becoupledto their respective reel drive shafts by providing a' frictionalcoupling connection between acollar member, such as collar of'sufficientlywide diameter having'an upwardly-facingfriction-surfacedesigned so'that 8 when areel is seated onthe shaft"end; the weight of the reel will establish a frictional couplingconnection with the facing friction material layer of the underlyingcoupling roller 63-.

Reel t t-is similarly supported-on a-similar seating disc 63 of anotherreeldrive shaft 88' which in the arrangement-shown in Fig. 1 forms arevolving part of another electric motor 69 supported underneath the toppanel in the same manner as'the-elements of the motor 64 which serves asa revolvable support for the reel 32. Through the medium of the threeelectric motors 5|, E55, '69, the driving shaft of the supply reel- 32and'the take-up reel 33 are intercoupled with the driveme'chanismincluding motor 51 of the constant speed normal forward drive capstan3'1, thereby assuring that there is at all times available a magneticfiuxor generally a-iiuid coupling medium as a coupling interconnectionbetween the several mechanical elements of the" driving mechanismthrough which forces are applied to the'recording medium, such as thetape 3|, as it is being impelled at a lowspee'd, such as eight inchesper second, on the take-up reel during a forward record transducingoperation.

As indicated in Fig. 1, the capstan roller 3'! with its fly wheel Edmay'be mounted to revolve on the shaft which is held affixed to a mountingplate 55 which is secured, for instance, through a plurality of spacerrods, not shown, to theunderside'of the panel'wall along which the reelsand the other exposed elements of the driving mechanism are located inexposed positions. The motor 5| is suitably affixed tothe underside ofthe mounting plate Sii so that the exposed upper shaft end of the motorshaft 52 projects through a hole' in the mounting plate and faces aperipheral portion of the rubbertired coupling'pulley'ES throughwhichthe shaft is coupled to the metallic periphery of the nv wheel 54'. Thefloating coupling pulley 53' is mounted in'a manner similar to theconventional mountings of' the floating coupling pulleys in phonographdrives.

As indicated-in Fig. 1,:the coupling pulley 53 is rotatably mounted on ashaft post 56 held affixed to a plate-like slider member 51. The sliderplate 51 is slidingly interconnected in a conventional way withapertures 58', 58l of the motor mountingplate 5i! and is biased, as byatension spring 59', connected between a fixed portion of the slider 5"]and a fixed portion of the mounting plate 5ilsoas tomaintain the rubbertire of the coupling. pulley 5-2 in coupling engagement withthe motorshaft 52 and the fly wheel 54 for transmitting thereto and to thecapstan 3i a rotary motion which causes the capstan roller 31 toimpartto the recording medium or tape 3 l the required flutter-freelowconstant speed, the rubber-tired coupling pulley with the fly wheel St-serving as a filter for filtering outany' non-uniformities of themotion transmitted by the motor 5!.

Ina commercial embodiment of the driving mechanism of theinvention-shown in Fig. 1, the threemotors 5i; 6d, GQ-ai'e standardhigh-speed inductionmotors of the type commonly used in small turntabledrives; In this driving arrangement, the shafts of the tWomotors 64; 69form revolvable suppor ts -fo'nthe two reels 32, 33 and theb'earingsof'the'two motors 6'4, 69 serve as journalling supports-fortheshafts 61, 68 0f the two reels.

The surface of the capstan roller" 3-! isprovidedwith a' surface la'yerof I friction -matrial,

such as Corprene or felt. When the magnetic recording medium 3| is madein the form of a tape of non-magnetic material, such as paper or plasticor resin material, an impelling or capstan roller 31, of an inch indiameter, will establish a good coupling driving engagement with suchtape for driving it at a constant speed if the tape encircles about ormore of the periphery of such impelling roller. As shown in Fig. 1 ofthe drawing, a record track engagement with only about one-half of theperiphery of the impeller roller provides suitable constant speeddriving engagement with substantially no slippage.

As explained before, the driving arrangement for the recording medium isso designedas to assure that when the magnetic recording medi; um, suchas the flexible thin tape 3| of limited strength is impelled along thenormal forward path 3| F at a slow speed by the driving forces impartedthereto by the capstan roller 31, the portion of the tape moving fromthe supply reel' 32 past the erasing and recording heads'lli, 42' to itsposition of engagement with the capstan roller 3'! is subjected to suchsmall tension forces that they are insuflicient by themselves to maintain stabe coupling engagement between the pole faces of the twomagnetic heads 4|, 42 and the facing portions of the moving tape 3|bridging the pole gaps of the two heads.

In accordance with the invention, stable contact conditions between thepole faces of each magnetic head 4|, 42 and the portions of the movtivecontact engagement with the pole faces of I each magnetic head bridgingthe pole gap region to assure stable flux interlinkage between thewindings of each magnetic head and the magnetic particles of therecording medium bridging the gap. i

. As indicated in Fig. 1, each of the holder pads 8| is mounted on aseparate lever arm 82 pivotally mounted at 82-| and subjected to abiasing action as by a spring 823 so that when each lever is su jectedto actuating forces exerted thereon by links 83, respectively, the twolevers are actuated to bring their respective ho der pads 8| intoengagement with the outwardly facing side of the portions of the movingtape 3| facing the pole faces of the two magnetic heads 4|, 42 to assurepositive and stable contact engagement between the pole faces of the twoheads and the magnetic particles of the moving recording medium,notwithstanding the small tension forces to which the moving recordingmedium is subjected.

As indicated in Fig. 1, each of the hoder pads 8| is normally held bythe biasing means 82-3 away from the facing pole faces of theirrespective magnetic heads 4|, 42 so as to leave open a substantialchannel space 84 between each pad and the facing magnetic head forenabling ready placing or threading the tape or, in general, therecording medium 3| a ong the path of the normal forward reeling motion3|--F as well as ready removal or unthreading of the tape,

two'biasing springs 823 associated with each' In other words, undernormal conditions when no normal forward reeling operation is carriedon, the entire forward reeling path 3|-F along which the recordingmedium or tape is guided from the supply reel past the transducer headsand the capstan roller 3'! to the take-up reel is open and forms a free,relatively-wide channel into which the tape may be placed or from whichit may be removed. However, as indicated diagrammatically in Fig. 1,each time the drive control mechanism is actuated to bring into action anormal forward reeling operation by actuating, for instance, the forwardpush rod 12 to the inward position, it will operate the lever '|2-D toexert through a link connecting it to the two links leading from the twopad levers 82 associated with the two magnetic heads, for cans-- ing thetwo pads 8| to be brought to their operatedposition in which each padholds a por tion of the tape in positive stable coupling engagement withthe facing portion of the respective magnetic heads M, 42.

' Foolproof operation of this mechanism is made possible'by interposingin each of the two links 83 through which the control lever "i2-D iscon-- nected to the two pad operating levers 82 a spring 83-4 sodesigned that when the two links 83 are actuated by the actuation of thecontrol'leve'r '|2D to the operated position, the two springs 83| willbe subjected to sufficient tension for overcoming the biasing forcesexerted by the pad lever and cause the two levers 82 to be 09-" eratedfor bringing their respective pressure pads 8| into the proper contactengagement position in which they hold portions of the tape in positivestable engagement with the facing pole faces of the two magnetic heads.

In a practical form of recording mechanism of the type showndiagrammatically in Fig. 1, each' end of the recording medium 3| made inthe form of a thin flexible tape of the type described above isconnected to the inner core or drum 34 of each reel by inserting the endof the tape'into an axial slit formed in the reel core wall and thenturning the reel until one convolution of the tape retains the insertedtape end in its position on the exterior of the core, at least one sidewall of each reel being provided with a generally radial opening or'slit so as to make it possible to grip the end of the tape broughtagainst the open periphery of the reel and place the gripped end of thetape in the slit of the reel core 34.

When carrying on reeling operations with such reel and tape arrangement,the end of the tape will automatically be pulled out from the reel fromwhich it is unreeled when the full length of the tape has beentransferred to the reel on impelling forces is energized only after themo tion of the tape has been initially started by momentary operation ofa starting control element so as to subject the portion of the tapemoving toward the reel on which it is reeled to an initial tensioningforce sufficient to move a limit control member, such as limit members38, 39 from the non-operated positions in which they are shown to anoperated position in which they perform a control action establishingthe reel im pelling conditions under which the motor and the 11 driveconnections are maintained to continue the reeling operation untileither the drive control arrangement has been stopped by the actuationof a stop control member or until the whole length of the recordingmedium or tape has been transported from one reel to theother.

In a practical form of reeling mechanism of the type showndiagrammatically in Fig. 1, the two limit control members 33, 39 aremade in the form of elongated guide members either as a smooth rod or asmall-diameter roller mounted on a roller shaft, the limit members 38 or39 being carried on the free end of an arm 38-4, 39-4, respectively,pivotally mounted so that the forces exerted by the moving recordingmedium or tape 3| on the limit members 38, 39 as it moves thereover willtilt the limit arm from a non-operated to an operated position foroperating limit control means indicated in Fig. 1 by the two limitcontrol switches 38-FL and 39-RL, respectively.

One form of selective reeling control arrange-'- ment utilizing the pushrod mechanism T9 of the type described in connection with Fig. l, oranalogous forms of such selective control mechanisms will now bedescribed by reference to the circuit diagram of Fig. 2. As shown inFig. 2, the capstan or constant speed drive motor 5|, the supply reelmotor 64 and the take-up reel motor 69 are arranged to be energized byelectric energy from a conventional alternating-current domestic supplysource indicated by supply line conductors l-P, 2P, respectively, aswitch 9| providing a connection between the power supply leads and thecircuits through which the drive control arrangement controls theenergization of the several motors. There is further shown a suppl lineconductor 2--Q which is connected through a relatively high impedancerectifier 92 to the supply line conductor 2P for making it possible toselectivelv s pply the windings of the reel sh ft motors 64, 69 with aD. C. current of a predetermined magnitude in accordance with theprinciples of the invention described hereinafter.

Fig. 2 shows also t e port ons of the several push-button rods H. "2,13. 14, I 1 and a set of switches Tl-C, 12C. l3-C, 14-0, 15--C, I -Chich are actuated to the operated po ition when t e respe tive p"sh rodsa e actuated to the n"'a d operated pos tion in the manner describedbefore in onnect on with the pu hrod control mecha ism in of Fig. 1.There are also show portions of the two l mit co trol mem ers P8. 9 witht e fnvwald l m t swit h 38FL and the rewind limit switch 39 R J whichare o erated to the operated pos t on each time the respect ve limitcontrol member 38, 39 has been actuated from the released position to afle ed oper ted position by the tension applied b the moving ta e to therespective limit control members 38, 39.

In the circuit diagram of Fig. 2. it is assumed that the reeling mechanim is at stand still, the stop switch Ii -C being sho n in the operatedposition held by the stop push rod M which is retained in the operatedposition in the manner indicated in Fig. 1. In this operating conditionof the control mechanism, all other push rods H to T4 and 16 will be inthe relea"ed position shown in .Fig. 1 and their respective associatedswitches II-C, l2-C, 13-0, M-C and 'i6C will be in the released positionas shown in Fig. 2. Furthermore, since in this standstill condition ofthe mechanism the recording medium or tape 3!;

12 is notmoving, it will not be subjected to any tension and, as aresult, both limit switches and -39--RL will be in the releasedcondition which they are shown in Fig. 2.

It should be noted that the recording device of the type shown in Fig. 1may be arranged so as to make it possible to reel the recording mediumin forward direction on to the take-up reel 33 at the same fast rate asduring the rewinding operation, by providing a limit member in the formof a roller revolvably mounted on a fixed shaft 49-4 and placed so thatwhen the recording medium 3| is led from one reel to the othereither-along the slow forward patch indicated by the dash-four-dot line3il or by way of the fast rewind or forward path indicated by thedash-five-dot line 3l5, a suflicient peripheral region of the roller 55will be engaged by the moving tape or recording medium 3! as tofrictionally rotate the roller 43 and cause a projecting arm 4E2 of theroller dB to actuate either a forwardlimit switch 38FLL or a rewindlimit switch 39-RLL from the normal non-operated position to a flexedoperated position in a manner analogous to that described before inconnection with the forward limit switch 38-FL and rewind limit switch39-RL.

When using such limit control means or limit switch arrangement. the twolimit control members 38, with their a sociated limit switch are omittedand replaced by the limit control member st'with the associated limitswitches 33RLL, SEE-FLL. These limit switches as well as all otherswitches of the control arrangement 19 are of the spring-blade typewhich return, when released, to the non-operated position in which theyare shown in Fig. 1. except for the operated stop switch l5C which isheld by the locked push rod '55 in the o erated position.

To facilitate the threading of the tape along the normal forward recordtransducing path 3|-F it is desirable to subject the tape to a verylimited small restrain as it is being pulled from the supply reel 32 andplaced along the forward guide path 3i-F between the channels 84 infront of each of the recording heads 4!, #12 and then around the cap tan31 and over the forward lir it member 38. and the tape end placed n theretainer slit of the take-1 p reel 33. Such limited restrain may beapplied by applying a limited brakinforce to the reel shaft iii of thesupply reel. In Fig. 1, such braking force is shown ap lied by the brakepad 62 engaging the "eating collar of the reel shaft 6! described above.However, in lieu of mechanical braking means 5-2, such limited brakingforce may be ap lied to either reel shaft 6| or reel shaft 68, ifdesired. by supplying to the windings of the t o motors 64, 69 a smalldirect component whenever the recording mechanism is in the standbypo"ition, with the stop push rod in the inner operated po ition in whichit is shown in Fig. 1 corresponding to the operated position of its asociated stop switch l5-C.

Fig. 2 also shows a portion of the recording medium or tape 3| moving inthe normal forward direction 3lF past the erasing head Al and the recordtransducing head 42 as well as the recording control switch 43 and therecording and playback circuits which are controlled by the o eration ofthe recording playback switch 43, in combination with certain contactorelements of the switches operated by the push rod 15 and the normalforward limit switch 38FL.

Other features of the recording and drive control arrangement of theinvention will now be described in connection with the followingdescription of its operation:

When the stop push rod 15 is in it inward operated position in which itis shown in Figs. 1 and 2, the drive mechanism of the recorder is in astandby position and the recording medium 3| will be at standstill. Inthis condition, the reels 32, 33 may be removed from their couplingengagement with their respective reel shafts or replaced thereon.Furthermore, in this standby condition, the tape may be threaded alongthe forward path 3|F for a slow forward drive recording or playbackoperation indicated by the dash-double-dot line. In such standbycondition, the recording medium may be also removed from its slowforward path 3|F and placed either on the fast rewind path 3|R or 3|-5or in the fast forward path 3|-4 or returned from any one of these pathsback to the slow forward path 3|-F or the like.

When the stop rod I is in its inward position, it actuates theassociated stop switch 15 C to open t e energizing circuit leadin fromthe supply line conductor 2-P to the continuation thereof 2P| throughwhich the individual motors 5|, 64. 69 niav be selectively en rgized.one terminal of each of t ese motor windings being connected to t esupnlv line conductor |-P of opposite polarity. The sto switch |5C mavbe provided with two add t onal similar contacts for connectin therectified l). C. supplv line 2-Q through suitable current limitin resitors to the windings of the sun ly reel and the take-up reel motors soas to subject them to a very sli ht braking action to facilitate the treading of the tape in the manner ex lain d abo e. Ho ever, for t e sakeof simplicitv, these obvious circuit connections have been omitted fromFig. 2.

Slow forward operation Assuming that the recording medium or ta e 3| isthreaded along the slow forward path 3 |F, a playback operation for plaing back a previously made record or a recording op ration may beinitiated at any time after fir t actuatin the slow for a d pu h rod 12and its as ociated switch 72C to their in ard. or operated positions.The actuation of the slow forward pu h rod 12 to the operated positionreleases the stop rod 15 to the non-operat d -o ition, thereby caus nits u h rod switch 15C to clo e its contacts and connect the motorenergizin line ZP| to the energy supply lead ZP. As shown in Fig. 1. theslow forward push rod in its inward operated position actuates thecontrol lever l2-D to the operated osition in which it transnuts throughlinks 85 and 83 actuating forces to the two pad levers 82, the ebybringin their pads 8| into a position in which they maintain theportions of the recording medium or tape 35 facing the pole gap regionof the two magnetic heads 4|, 42 in stable contact engagement with thepole faces of the magnetic heads.

In its inward operated position, the slow forward push rod 12 actuatesits push rod switch lZ-C to establish the following motor energizingcircuits provided the forward limit switch 33FL has likewise beenactuated from the release position in which they are shown in Fig. 2 tothe operated position:

In its inward flexed position, the slow forward push rod switch '|2Ccloses an energizing cirwhich complete the motor energizing connection,

to the motor supply lead 2-P|.

It should be noted that actuation of the forward push rod 12 and theassociated slow forward switch 12-0 to the operated position does not byitself complete the circuit required to energize.

the constant speed drive motor 5| and the takeup reel drive motor 69,because the forward limit switch 38 was released during the previousstandstill condition since the tape or recording medium 3| was nottensioned and permitted the biasing action of the contact springs of theforward limit switch 38FL to return the contact springs to thenon-operated position in which contacts open the energizing circuit tothe two motors leading from the disconnectable power supply lead 2-P|.However, when the slow forward push rod 12 and its associated switch'|2C have been actuated to the inward operated position, it is merelynecessary to momentarily actuate the start switch '||C for momentarilycompleting at its contacts I a circuit which shunts or bypasses thestill open contacts I of the forward limit switch 33, so that the twomotors 5|, 69 are instantaneously energized and start the reelingoperation as soon as the starting switch H has been actuated to theoperated position, whereupon, the forward limit switch 38--FL isactuatcd by the tensioned recording medium or tape 3| to complete andmaintain the previously described circuit through which the two motors5|, 69 are energized in the manner previously described.

It should be noted that the starting switch 'H-C remains closed only aslong as the button of its push rod ll is held in its inward position sothat after momentary actuation of the push rod H it and its associatedswitch '||--C will automatically return to the released position inwhich they are shown in Figs. 1 and 2, respectively.

' As will be seen from Fig. 2, the circuit through which the constantspeed drive motor 5| and take-up reel drive motor 69 are energized, arecontrolled not only by the slow forward switch '|2C and the forwardlimit switch 38-FL, but also by contacts of the rewind switch 'MC andcontacts of the rewind limit switch 39RL, the purpose of thisinterlocked circuit control arrangement being explained hereafter.

' The slow forward reel operation just describedmay be stopped at anymoment by momentary actuation of the stop push rod E5 to the inwardoperated position, thereby automatically restoring the previouslydescribed standstill condition in which the operating elements of themechanism are shown in Figs. 1 and 2. Furthermore, if substantially thefull length of the recording medium 3| has been reeled on the take-upreel during the slow forward operation, the end of the tape 3|, uponbeing released from the supply reel 32, will release the forward limitswitch 38-FL from its flexed operated. position and cause it toinstantaneously open at its contacts the energizing circuit from thedisconnectable power supply lead 2P| to the two motors 5|, 69.

Rewind operation .A slow rewind operation may be started at any momentduring the progress of a slow forward re'el operation along the path 3l-F by actuating the rewind push rod 1d and its associated rewind switchl-:-'C to the inward operated position. However, if it is desired toeffect a fast rewind operation of the recording medium, the slow forwardreeling operation has to be first brought to a stop by actuating thestop rod 15 with its stop switch l5C to the operated position in whichthe reeling operation is stopped.

Thereupon, the tape or recording medium 3| which is now released fromany tension is removed from its position along the slow forward reelingpath 3IF and placed along its fast rewind path 3l-R so that a portion ofthe tape or recording medium it passes over the rewind limit member 39.Thereupon, a fast rewinding operation may be started by first actuatingthe rewind push rod W and its switch 14C to their inward operatedposition and momentarily actuating the starting push rod H and itsstarting switch 1 |C to the operated position.

When the rewind push rod 14 with its rewind switch 7l-C are actuated tothe operated flexed position, respectively, there are established thefollowing circuits for energizing the supply reel motor '64 for carryingon a fast rewinding operation:

The operated contacts I of the rewind switch 14-43 and the operatedcontacts 2 of the rewind limit switch 39RL complete an energizingcircuit from the disconnectable power supply line 2Pl to the supply reelmotor 64. In order to cause the rewind limit switch 39RL to actuate itscontacts to the operated position in which its contacts 2 complete theenergizing circuit for the supply reel motor 54, it is merely necessaryto momentarily actuate the starting push rod H and its switch ll- C tothe operated position in which its contacts 2 by-pass or establish aparallel circuit around the contacts 2 of the rewind limit switch 39-RL.

During the rewinding operation, the take-up reel 33 is under norestraint and the energized supply reel motor 54 will now impart to thesupply reel 32 its full speed, thereby causing the tape to be rewound ata very fast rate. In the practcal recording arrangement based on theprincipes of the invention utilizing reels seven inches in diameter forstoring a magnetic recording tape sufficient to make a record of half anhours duration, the full length of such tape will be rewound on thesupply reel 32 within about one minute by using the reelng arrange mentof the invention of the type described above.

Since the recording medium .or tape moves at a very high speed duringsuch fast rewinding operation, it is important to provide safe-guards toassure that the tape or recording medium is not torn and that otherw'seno damage is done. According to one phase of the invention, one suchsafe-guard is provided by assuring that when the full len'zth of thetape or recording medium 3! has been reeled on the suppy reel 32 duringa fast rewinding operation, the reeling operation is automaticallystopped and braking means are automatical y applied to the shaft of thesupply reel 39 on which the full length of the tape has now been'rewound.

Thus, at the end of a rewnding operation, the rewind limit switch 39-RL,on being released from the operated position, will automatically returnto the non-operated position while the rewind switch l t-C is stillretained in the flexed operated position by its inwardly latched pushrod M. In this operating condition, a direct current is suppied from thedirect current line 2Q by way of the re eased contacts 2 of the rewindlimit switch 3lRL and therefrom through the operated contacts I of therewind switch 'l4C back to the windings of the supply reel motor 64, theD. C. energizng circuit being completed through the connection of themotor windings to the power supply lead l-P which is at all timesconnected thereto and which, in conjunction with the rectifier 92,supplies the required direct current to the windings of the motor M.

Squirrel-cage induction motors are very effective braking means when thewinding of such motor is supplied with D. C. Conventional squirrel-cageinduction motors of the type used in turn-table drives may be readilystopped by the braking action exerted on the squirrel-cage inductor bythe magnetic field interlinking the stator with the rotor of the motorwhen the winding of such induction motor is supplied with a directcurrent of about milliamperes.

According to another phase of the invention, an additional safe-guard isprovided in case, during the progress of a fast rewinding operation, anyone of the other push rods or controls of the driving mechanism havebeen actuated either accidentally or delberately, for instance, byactuating the stop push rod button 15, for stopping the fast rewindingoperation by releasing the rewind push rodand its associated rewindswitch lQC to the non-operated position, by bringing about automaticapplication of brak ng forces to the shaft of the take-lip reel 33 whichis now rotated at a high speed as the recording medirm is reeled offtherefrom on to the supply reel 32. e

As shown in Fig. 2, when the rewind switch 14 is released during a fastrewinding operation and opens at its contacts I the alternating currentpower supply to the supply motor G l, its released contacts 2,conjunction with the still flexed contacts of the rewind limit switch,completes a circuit for supplying direct current from the direct currentsupply lead 2Q to the take up motor 69 for applyinr thereto brakingforces which bring it promptly. but in a gradual manner, to a stop, asexplained above, the rewind limt switch 39-RL being retained in theoperated flexed position as long as the momentum of the rotating supplyreel with the tape or recording medium that is being reeled thereon at afast rate, maintain the recording medium under tension.

The safe-guards just explaned are effective not only when the stop pushrod 75 with its stop switch l5-C have been actuated to stop a fastrewind operation while it is progressing, but also when any one of theother push rods, such as l2, l3, 76 of the control mechanism l9 andtheir switches are actuated to their inward position during the prowessof a fast rewinding operation, thereby releas'ng the rewind push rod 74and its switch to the non-operated position.

Fast forward Since the reel of a recording mechanism of the typedescribed above is capable of storing a record of long duration, it isfrequently desired to perform a fast forward reeling operation forreaching a particular portion of the record pre- I 17 yiously made onthe recording medium. With the recording arrangement shown in Fig. 1, afast forward reeling operation may be carried on by first leading thetape passing from one reel to the other along the path indicated by thedashfive-dot line 3l--5 over the revolvably mounted roller 40 so thatwhen the tape moves along the path 3|--5, it will, through itsengagement with the surface of the limit ro'ler 40 cause its arm tooperate the associated forward limt switch 38--FLL to the operatedposition, this switch having the same contacts and operating in the samemanner as the forward limit switch 3B-FL shown in Fig. 2 in connectionwith which such fast forward operation will be described.

To start a. fast forward reeling operation, the fast forward push rod 73and its associated switch have to be actuated to the operated or inwardposition, whereupon momentary actuation of the 7 starting push rod withits starting switch 'HC fast rate as the fast rewinding operationdescribed above: 7

The fast rewind energizing circuit for the winding of the take-up motoras is established by the closed operated contacts I of the fast forwardswitch 13C in conjunction with the operated 3 contacts 3 of the forwardlimit switch 3BFL through which the winding of motor 68 is connected tothe disconnectable power srpply lead 2-P!, the operated contacts 3 ofthe starting switch IL-C establishing a by-pass or a parallel circuitaround the contacts 3 of the forward limit switch 3SFL to momentarilyenergize the takeup reel motor 69 and start the fast reeling operationso that the now tensioned tape or recording medium 3! shall cause theforward limit switch 38FL to be actuated to the operated position.

Because of the extremely fast forward reeling operation, the recordingdevice must be provided with safeguards for safe-guarding againsttrouble in case the rewinding operation is stopped by the completion ofa fast forward reeling opera tion when the end of the recording mediumor tape 3! is released from the supply reel 32 and the full length ofthe recording medium has been transferred to the take-up, and in thecase when the progress of a fast rewinding operation has been stoppedeither by momentary actuation of the stop button or push rod l and itsswitch l5-C or by the m mentary actuation of any one of the other pushbutton rods 12, it. it, thereby releasing the fast forward push buttonrod and its switch from the operated position.

When, the course of a. fast forward reeling operation, the full lengthof th recording medium or tape 3! has been transferred from the sup plyreel 32 on to the take-up reel 33. the released forward limit switch3.!-FL disconnects at its contacts 3 the disconnectable power supplyline 2--Pl from the energizing circuit leading therefrom by way of theclosed operated contacts 5 of the fast forward switch to the windingofthe take-up reeling motor 69, in its released condition this samecontact 3 of the forward limit switch 38-FL now connects the circuitleading from the winding of motor 69 to the D. C. supply line 2-Q whichnow sends direct braking current to thetahe-uo motor, thereby bringingit and the take-up reel 33 with the recording medium fully reeledthereon to a prompt but gradual and controlled stop.

On the other hand, if, during the progress of a fast forward reelingoperation, either stop push rod with its switch I5C is actuated to stopthe reeling operation, 01' if any one of the other push button rods 12,M, 15 are actuated to the inward position, thereby releasing the fastforward switch from the operated position while the forward limit switch38FL is held in the operated position by the tape which is being reeledat a fast rate on the take-up reel-circuit connections are automaticallyestablished for supplying to the winding of the supply reel motor 64 aD. C. brakingcurrent, thereby bringing it to a prompt but gradual andcontrolled stop and thus stopping the progress of the fast reelingoperation.

The braking circuit connections for the winding of the supply reel motoriii are completed by the operated contacts 2 of the forward limit switchin conjunction with the released contacts 2 of the fast forward switch'|3-C as well as by the contacts of the auxiliary switch $3-F which inthis condition establish a connection between the direct current supplyline 2-Q to the winding of the supply reel motor 64, the energizingcircuit beingcompleted through the other power supply line iP whichremains connected to the motor as long as the main power switch 9! isclosed. The auxiliar switch sit-F is so interlocked with the operationof the fast forward reel control elements and the slow for-ward controlelements, namely the fast forward push button 33 with its switch 'l3Cand the slow forward push button 12 with its switch 'i2C, as toautomatically assure that the braking action is applied to the supplyreel shaft or to the shaft of motor it only when a fast forward reelingoperation is carried on.

Various means may be provided to automatically assure such interlockingrelationship between the operation of the auxiliary switch 93F and theoperation of the slow forward and fast forward reeling controls. For thesake of simplicity, one form of such interlocking arrangement is shownin Fig. 2. A switch control arm 93, pivotally mounted at 93-4, whichactuates the switch 93-46 is movable either between the position shownin which it holds the contacts of switch 93-? closed or the dotted lineposition 93-0 in which switch 93-F is held open.

As shown in Fig. 2, a two-section toggle arm 93-2, the sections of whichare mounted for telescopic movement relatively to each other, isconnected between a fixed pivot pin 93-3 and a pin 93-4 of the switcharm 93, the two sections of the toggle arm 93-4 being biased as by anencircling compression spring 93-5 so that each time the switch arm ismoved in either direction past the center position between its pivot93-I and the fixed toggle arm pin 933, the switch arm will be broughteither to the ful-line position in which it closes its switch 93-F or tothe dotted-line position in which it opens its switch contacts.

Means are also provided to automatically actuate the switch arm 93 withits switch contacts to the position in which it opens the contacts 93-F'whenever the slow forward control button and switch are actuated to theoperated position, and to automatically actuate the switch arm 93 withits switch contacts 93-1? to the closed position whenever the fastforward reel control means, such as the push rod 13 with its switch13-0, are actuated to the operated position.

For the sake of simplicity, this automatic control is shown in the formof two auxiliary arms 12-1, 13l, each held biased by a conventionallyindicated spring against a stop pin 12-3, each arm having pivotallyconnected to its end a pawl 72-4 riding on a facing cam surface portionof the switch arm 93 so that when the respective arms 12-1, 13-! ispivoted away from its stop pin, its pawl will engage one of the twoteeth 93-6 of the switch arm so as to throw it from one position to theother.

The two levers 72-4, l3-I are arranged to be actuated by the two pushrods l2, 13 of the slow forward and fast forward reel control means insuch manner that when the slow forward push rod 72 is actuated it willactuate the lever 12-i and cause it to throw the switch lever 93 fromthe full-line position shown to the dotted-line position in which itopens the auxiliary switch contacts 93F if the switch arm 93 with itscontacts 93-F are not already in this open contact position.

In a similar manner, the auxiliary switch control lever 13-4 isassociated with the fast forward control means or push rod 13 in suchmanner that in the event the switch lever 93 is in the dash-lineposition 939 in which switch 93 .is open, the actuation of the push rod13 will operate the lever 'I3| in such manner as to throw the switch arm93 with its switch 93F from the dash-line open position to the full-lineclosed position in which it is shown.

The roller limit member 49 with its associated switches 38-FLL and39--RLL may replace both limit control members 38, 39 and their switches38-FL, 39-RL to provide a more simplified construction. The single limitmember 49 may be used for controlling either a forward or reversereeling operation which may be either slow or fast speeds. With sucharrangement the surface of the roller 49 is made smooth enough to reducethe friction against the tape so as not to unneccessarily decrease thespeed of the high speed reeling operations either forward or rewind. Avery smooth surface still provides enough friction so that the movementof the tape rotates the roller 49 together with projecting arm 492 farenough to operate the actuating members of the switches 39FLL and 39RLL.As shown, for a forward slow reeling operation the tape is threadedthrough channels 84 around the capstan roller 3'! and then over controlmember 40 along the guide path 3l4 and onto the reel 33. Slow rewindingmay take place along the same path if it is not desired to rethread thetape, the capstan roller 31 and its mechanically linked structureincluding the coupling roller 53 and motor providing sufficient inertiaand friction to hold down speed of the rewind even though the windingsof motor 5! are not activated. However, to prevent any tendency for theslow rewinding operation to unduly increase in speed, the rewind pushbutton switch IQ-C may be provided with another set of contacts foractivating the windings of motor 5! with a small amount of D. C. toprovide a further braking force.

The slow rewind is very useful in helping to locate a desired portion ofa long record inasmuch as the fast reeling operations are effected witha minimum of friction or other braking forces and proceed at extremelyhigh speed with the motors 94 or 69 operating at substantially theirmaximum R. P. M. The slow rewind, of course, is also useful when it isdesired to repeat a nearby portion of the recording since it is notnecessary to rethread the tape.

The switches 38-FLL, 39-RLL may be identical with the illustratedswitches 38-FL and 39-RL, respectively. The contacts 5 of forwardlimitswitch 38FL, as shown in Fig. 2, parallel the supply motoractivation circuit contacts 2 of rewind limit switch 39-RL makingpossible the initiation of a slow rewind without operation ofstarting-push button shaft H since it enables initiation of theoperation of supply reel motor 64 Without prior activation of reverselimit switch 39RL. The momentary initiation of supply reel motor 94performs the same function as momentary operation of the starting pushbutton shaft H in the construction using a single limit control member49 and the contacts 5 of switch 33-FL may be omitted from such aconstruction. However, in the modification using the separate forwardand reverse limit members 38, 39, respectively, the contacts 5 of switch38-FL are very useful in that they make it unnecessary to thread thetape 3! over the reverse limit member 39 to obtain a slow rewind.

It is desirable to effect a slow forward winding operation as well as ahigh speed winding with minimum braking forces applied by the brake pad62. With such minimum braking forces the slow forward winding can beeffected with a minimum of tensioning ofand friction against the recordtrack and the high speed winding can be effected at the highest possiblespeed.

A home recorder as described above is capable of making high qualityrecords of symphonies or other desirable entertainment and of makingpermanent records of conferences, legal agreements, contracts, etc.under the operation of any layman having an extremely low level ofmechanical information or ability. Such recordings may be preservedindefinitely and may be played back any number of times withoutappreciable effect on the recording. There may also be obtained at someexpense commercially prepared recordings, such as musical master works,and these as well as other recordings could be irreparably lost bymerely reeling through the machine for a short time with the magnetichead set for erasing or recording. It may be particularly desired topreserve such a valuable or expensive recording and to guard againstaccidental or inadvertent damage to the record, such as obliteration orsuperimposition of another recording.

The apparatus of Figs. 1 and 2 provides two safeguards against suchdamage. One safeguard is the push button switch arrangement i9 whereintwo separate push buttons are provided, namely, the slow forward pushbutton 72 and the record push button it, both of which must be operatedat the same time and held down in order to set the apparatus for arecording operation. These two push buttons T2 and T6 are not adjacentand are not easily or accidentally operated at the same time. Evenslight differences in the time of operation will cause the lateroperated push button to release the earlier operated push button. Onlydeliberate and careful push button operation will set the apparatus foreither an erasing or recording function such as IWOLlld damage arecording. The push buttons l2, '15 may be biased toward theirinoperative positions by springs of unequal compression so as to make iteven more diflicult to inadvertently push them both simultaneously totheir operative position. The recording push button 79 together withswitch iii-c does not control any motor circuits but it does interruptthe 13+ power supply to the oscilator '47 as well as the additionalrecording amplifier 49, thus assuring that no erasing or superimposingsignals are present. The switch I6C also at its contact 20 opens thecircuit to the recording winding so that even with the switch 43 in therecord position in which it might accidentally be held no recordingcurrents are supplied to the transducing head. Another safeguard isprovided by the biasing of switch 43 in the playback position by thespring or other tension member 43-2 as shown, making it impossibleto-inadvertently leave the switch 43 set for recording. The pivotedlatch member 43-3, illustrated as operated by the lever I2--D actuatedby the inward operation of forward push button 12, engages a projection434 on the switch 43 and latches the switch 43 into record position whenthe forward push button I2 is in its inward operating position. Theswitch 43 can only be retained in the record position if it is moved tothis position simultaneously with or after the inward operation offorward push button I2. Attention is a so called to the fact that theforward limit switch til-FL at its contacts 4 establishes the circuit tothe erasing head 4I so that erasing is impossible except when the tapeis driven in a forward direction.

A top view of a practical construction for the magnetic recorderdescribed above is shown in Fig, 3. The supply and take-up reels 32, 33,respectively, are shown as pivotally mounted on vertical shafts 6 I, 68.The magnetic heads 4 I, 42, the capstan roller 31, and the forward limitcontrol member 38 are disposed in the region between the two reels. Thecover plates I00, IIII are placed at approximately the level of the topof the rees and are shown so shaped and disposed that very littleclearance is provided between the reels and the cover plates, themagnetic heads and cover plate I02, and the capstan roller and coverplate is I. The cover plate IIJI] also extends over the forward limitcontrol member 38. Along the path that the tape is to be threaded toengage the magnetic heads, capstan roller and fonward limit controlmember, a relatively wide channel is provided by suitably shaping andspacing the member plate iIlI. With such construction the only placethat the tape can be conveniently placed is in the channels provided,which automatically insures the proper threading of the tape. The coverplate I! covers both pads BI when they are in retracted position so thatthere is no possibility of inserting the tape so as to jam against orentangle in the pads (II or pad lever arms 82. The magnetic heads BI, 82may be of the type described in the application of Otto Kornei, SerialNo. 688,034, filed August 2, 1946, Patent No. 2,523,576, hereinbeforementioned and may be provided with covers as indicated. These covers maybe metalic and may be used as magnetic shields for the heads. A coverplate I62 is shown as placed over the rewind limit control member 33 andproviding very little clearings adjacent the supply reel 32. Anothercover member I04 is shown as spaced from cover member 'I 02 to define achannel along which the tape may be threaded for rewinding. The covermember I34 is also very closely spaced against the take-up reel 33. Thecover member I62 maybe made in tegral with the cover member IIlI, ifdesired. With the above construction any unskilled person can thread thetape either for forward reeling or for rewinding [Without anydifiiculty. To further facilitate the threading arrows and legends maybe placed alongside or in the proper channels as indicated. Care must betaken so that enough clearance is left between cover member IIII andboth reels as well as between cover member I02 and both reels so as topermit the passage of tape therethrough. This increased clearanceenables the tape to be lifted from around the capstan roller and theforward reeling channel, moved over and lowered into the rewindingchannel while the tape is partially mounted on both reels.

In the lower right hand portion of Fig. 3 is diagrammaticallyrepresented the controls for the apparatus, including the push buttonassembly I0, the knob of switch 43, the knob of a volume control, jacksfor plugging in various signal feed circuits, an on-01f switch as wellas a tuning eye for adjusting the level of the recording currents. Anyother desired controls may be employed, and any other arrangement of theillustrated controls may be made...

Fig. 4 as well as Fig. 3 indicates the reel construction. Both supplyand take-up reels are made of two side plates H8, H2 crimped andfastened together in the center, in the manner shown, as by welding. Theupper plate H2 is provided with a series of slits I I5 extending fromthe periphery of the crimped hub portion to adjacent the extreme edgesof the plate. Where the slits II5 meet the hub, the hub is cut away, asshown, to provide access for an anchoring short length of tape. Theslits II5 are made too narrow to admit a persons fingers, the tape beingengaged by bringing the end between the plates Hi], I I2 from theextreme edges with the fingers and threading the tape up and out throughthe outer end of one of the slits whereupon the end of the tapeprojecting through and above the slit may be grasped by the fingers, ledalong the slit from the outside down to the base of the slit where theend of the tape may be lowered into the cutout portion of the hub.Rotation of the reel to wind one turn of the tape around the anchoredtape end will firmly mount the tape for reeling either at high speed orlow speed.

In a fast reeling operation the reels rotate at such high speed that theuse of wide slits could easily cause someones wandering finger to beengaged by a slit and severely injured.

Figs. 5, 6 and '7 illustrate one form of magnetic head assembly that maybe used with the apparatus described above. A lower dished-out platemember I29 has mounted on its downwardly dished portion an approximatelycylindrical housing I 22, the lower surface of which is flanged for thereception of mounting screws, as shown. The cylindrical housing I22 hasits walls cut out at I24 to provide access to the interior in which ismounted a magnetic head. These circular magnetic heads described in theKornei application, Serial No. 688,034, filed August 2, 1946, issued asPatent No. 2,523,576 are suitable for mounting in the cylindricalhousing I22. Lugs I26 depending from the edges of plate member I20 formpivotal supports for shaft I21 on which is mounted a pair of arms I82.The arms I82 are so dimensioned that upon pivoting their upper ends willenter the cut away portion I24 of the housing I22. On the upper ends ofthe arms I82 are mounted the pads IBI which may be made of resilientsoft material, such as felt. When actuated by the link members 83 ofFig. 1 the arms are pivoted so that the pads I8I are brought against thepole portion 42I of the magnetic head. Springs I83 fastened to the undersurface of the plate member I20 bias the arms I82 in a clockwisedirection, as is best seen in Figs. 5 and 6. Although Figs. 5, 6 and '7show only one magnetic head mounted in a single cylindrical 23 housing,two such heads may be mounted side by side into housing members bothfastened to the same lower plate member 20. The cylindrical housing E22as well as the plate member lZil may be metallic so as to providemagnetic shielding for the sensitive magnetic heads, apertures beingprovided in the plate member E26 for passage of the electrical leads iiil connected to the windings around the magnetic core. The ends of shaft52? may be bent over, as shown in Fig. 7. to lock it in place. Theentire assembly of Figs. 5, G'and '7 may be mounted in the upper portionof the apparatus of Fig. 3, for example, the cutout portion I26 beingsituated at the level of the tape on the supply and take-up reels. Thepads IS! in their retracted position will then be covered by the covermember l'e-l, and the arms 182 will project below the tape channel andthe upper portion of the apparatus and may be operated from below bysuitable linkage with the .forward push button 72.

In Figs. 3 and 9 is shown a constructionwhich makes it unnecessary tomove the tape through separate channels for a slow forward and fastrewind reeling operation. This construction em ploys a capstan roller23; rotatably mounted on a shaft 255 on which also rotata-bly mounted apair of arms 2%, each carrying a guide pin 2%. Attached to the lowerportion of each guide pin is a rigid link 2- 53, as shown. Both links233 are connected to an operating lever 2:35 which may be pivotallymounted. The operating lever 24 5 may be spring biased so as to hold theguide pins 246 in a projecting position, such as is shown in solid linesin Fig. 8, where they hold the record track 35 away from the surface ofthe capstan roller 23? so that a high speed reeling operation may beeffected without rethreading the tape and without using a separate highspeed threading channel. Operation of the operating lever 245 isadjusted to retract the guide pins Edi] to the dotted line positionshown in Fig. 8 where the tape at is not held away and is permitted toengage the capstan roller 23? so as to establish and maintain a constantslow forward reeling operation. The guide pins 2 5i) should have a veryhighly burnished surface so as to effect the minimum frictionalengagement of the tape to permit high speed winding without unduetensioning of the tape and to enable the use of the minimum fast reelingpower. The guide pins 248 may also be pivotally mounted in their arms233. Another guide pin may be mounted so as to project through thebottom of the channel track and may be fastened to an operating lever248 pivotally mounted below the channel so that actuating of theoperating lever 248 will cause the guide pin 2t! to move in a slottransversely of the channel path." The guide pin 24'! is adjusted sothat whenretracted into the retracted position, shown dotted in Fig.8,the tape 3! is per mitted to contact the magnetic coupling portion ofeach of the magnetic heads 4i, 42 and when the guide pin is moved .toits operating position, shown in full lines in Fig. 8, the tape 3.! 'isheld away fr 111 and does not contact either of the magnetic heads 4!,52. The operating lever 25$ may also be biased to hold the pin 2 in itsprojecting operating position, both operating levers 245 and 2% may beconnected so as to withdraw the guide pins into their retractedpositions whenever the slow forward push button T2 is pushed to itsinward operating position.

Alternatively, the operating levers 245 and :248

may be reverselybiased was to hold their guide 1 pins in their retractedpositions, in which case the operating levers 245, 243 may be sodisposed as to be operated to project the guide pins into theiroperative position by inward movement of either the fast forward pushbutton 73 or the rewind push button !4. An idler pulley 268 may beprovided, as shown, to insure good contact between the moving tape 3!and the limit control member 40.

The apparatus of Figs. 8 and 9 may be used with a cover plateconstruction similar to that shown in Fig. 3, in which case the coverplates may be shaped to provide only a single channel used for both slowforward and high speed reeling. The cover plate should be so shaped asto overlie all the guide pins, as indicated by the dashed structures281, 252 and 203.

Means may be provided to automatically stop a forward reeling operationbefore the tape is completely unwound from the supply reel 32. Such aconstruction makes it unnecessary to anchor the supply end of the tapeafter the completion of a forward reeling operation. The rewinding maythen be accomplished by merely pushing the rewind push button 14 intoits inward operative position if the tape is to be rewound in the samechannel it is guided through for a slow forward reeling, as in Figs. 8and 9. With the construction of Figs. 3 and 4, the fast rewinding couldbe accomplished by lifting the tape from the forward channel, moving itover and lowering it into the fast rewind channel followed by inwardmovement of the rewind push button is. The automatic arresting of theforward reeling may be electrically accomplished by means of anelectrically conductive coating near the end of the tape that isanchored to the supply reel 32. The limit control member 49 may, forexample, be provided with two conductive portions in its surface spacedby a thickness of electrical insulation. A relay may be operated by thecompletion of the circuit through the contact surfaces oflimit controlmember 49 and the'conductive layer on the tape 3!. This relay may simplybe connected to operate the forward limit switch 38-FLL. The circuitsshould be adjusted so that the relay operation should effect theapplication of vsuflicient braking forces to the supply reel 32 to stopa fast forward reeling operation before the tape is completely unreeled.

.As an alternative construction the relay operating contact surfaces maybe placed on the limit control member 39, in which case the relay may beconnected to operate the limit switch 38-FL and the limit control member38 may be omitted entirely. If desired a similar relay may be used forstopping the rewind operation. These r lays .could obviously be modifiedto respond to any other physical characteristics of the tape, such asreflectivity, using photoelectric coils. When two such relays are usedthey may each be positioned to respond to the respective surfaces of thetape.

In Fig. 10 is illustrated a modified construction, similar to that ofFig. 8, in which the tape 3! moves along a forward guide path (ii-F anda rewind-guide path 3 I--R which do not require separate threadingoperation. The reverse guide path 3i-R includes a portion between thelimit control member 49 and an idler roller M5, and in this guide pathportion the tape passes adjacent to but not in contact with the magneticheads 4|, 42 and the capstan roller 31. Neither magnetic head 4| or 42is magnetically linked with the tape when the tape is in this rewindguide path 3IR. An arm 3l6 pivoted at M8 and having two rollers 34!]mounted at one end is mounted so that when pivoted the two rollers 340engage the tape 3| and move it from the rewind path 3l-R to the forwardpath 3l-F. In this forward path the tape now contacts the magneticallylinked portions of magnetic heads 4|, 42 and the tape is also pressedagainst the capstan roller 3'! by the two rollers 340. Only one roller340 is sufficient to establish good driving contact between the capstanroller 31 and the tape. If two rollers are used, care should be taken,as by mounting the rollers on independently swinging biased arms, toinsure that both rollers automatically assume positions of propercontact engagement when the rollers are moved into their projectingactivated position, shown in full lines in Fig. 10. The arm 3l6 may bebiased into its inactive retracted position, shown in dotted lines inFig. 10, and may be connected so as to be activated by inward motion ofthe slow forward push button 12. The arm 316 with its rollers may bemounted underneath a cover plate so that it is not visible and mayexpose the threading channel when it is in its retracted position. Coverstructures similar to those of Fig. 3 may be placed on the constructionof Fig. 10 as indicated by the dashed members 3M an 302. Fig. 11 showsanother modification of the invention in which only a single motor 45]is employed to impart the proper drivin forces to the capstan roller 31as well as the two reel shafts GI, 68. The motor is shown as driving thecapstan, roller 31 in a manner analogous to that shown in Fig. 1, twobelts being used to deliver power from a pulley mounted on the shaft 452of motor 45! to two separate clutches 460, MM. Each clutch 46c, 46!comprises two independently rotatable members 464, 465, member 464 beingshown as the drive member actuated by the belt, and member 465 being thedriven member and being fixed on the reel shaft 6! or 68.

The clutches may desirably be magnetic clutches wherein the member 464is secured to an internally mounted electromagnet 461 having anon-magnetic gap fill-extending around its periphery. Member 465 may beof highly conducting metal with a peripheral flange extending over andslightly spaced from the non-ma netic gap 410. A magnetizing winding 415is provided for inducing a magnetic flux in a nonmagnetic gap 410, thewinding leads being connected to brush contacts, as shown.

This clutch is of the type described in the Kellogg Reissue Patent No.19,270, dated August 14, 1934, and exerts-a coupling action between therelatively rotatable members 464, 465 when these members are rotating atdifferent speeds and when the magnetic flux as controlled by the currentin the winding 415 is induced across the gap 410.

Another feature of the recording apparatus of the invention is theprovision of means'for substantially instantaneously stopping the slowmercial announcement is to begin, and to resume the recording processwhen the desired portion of the program is continued.

Fig. 12 shows a portion of the apparatus which may be used for effectingsuch interruptions. Adjacent the periphery of the take-up reel 33 ispivotally mounted a stop lever 19 to which is affixed a braking pad 26.When the stop lever is manually operated to the braking position duringa slow'forward reeling operation it will immediately-stop the rotationof the take-up reel 33 inasmuch as the take-up motor 69 exertsvery'little torque and the brake pad is applying friction at a greatdistance from the center of rotation. As soon as the take-up reel stopsa very slight continued forward motion of the tape induced by continuedrotation of the capstan roller 31 causes slack to appear in the guidepath. This slack effectively removes the tape from contact with thecapstan roller and stops further forward motion of the tape. The stoplever I9 may be biased so as to provide a toggle action, as shown. Aswitch 2! may be mounted in the path of the stop lever so that when thestop lever is retracted from its braking position it actuates the switchto close its contacts and momentarily by-pass the contacts I of startingswitch I |--C. With this construction merely withdrawing the stop leverI9 from its braking position will start the recording process withoutthe necessity for operating the startingpush button Tl. The stop leverI!) may be relay op erated, if desired.

The expression magnetic record transducing as used herein in thespecification and claims is intended to mean either the operation of magnetically recording signals on a magnetic recording medium, or theoperation of reproducing magnetically recorded signals, or the operationof erasing magnetically recorded signals, or any combination of two ormore of these operations.

It will be apparent to those skilled in the art that the novelprinciples of the invention dis closed herein in connection withspecific exemplifications thereof will suggest various othermodifications and applications of the same. It is accordingly desiredthat in construing the breadth of the appended claims they shall not belimited to the specific exemplifications of the invention describedherein. v

I claim: 4

1. In a magnetic record transducing apparatus for transducing magneticrecords on successive elements of a moving tape-having a relatively widepermanently magnetizable record surface on one operative side and anopposite side of the same width, the combination comprising: guide meansarranged to guide said tape along an elongated guide path; a magneticrecord transducing head comprising a magnetic core provided with anoutwardly exposed magnetic-pole core face with said core extendingsubstantially entirely along one sideof said core face; a backingelement having a backing face for cooperation with said coreface;-said-core and said backing element being mounted for relativemovement between'a non-transducing condition in which said core faceseparated from said backing face for receiving therebetween said tape;and a transducing condition in which said core face and said backingface are biased to contact the opposite sides of one portion of the tapealong said guide path for pressing the operative side of the tape intostable magnetic engagement with said core face; said guide meansincluding power-energizable accuse.

impelling means selectively settable either in; a transducing settinginwhich the impelling means impels said tape. in a transducing manner,or-in non-transducable setting. in which said impel ling means impels:said tape in a non-trans ducing manner; and operating means operative inaccordance with the setting: of said. impelling means. for causing saidcore and saidbackingelement to be maintained in a .transducing conditionwhen said impelling means is in the transducing setting, and for causingsaid core and said backing: element to be maintained in, anon-transducable condition when said impelling means is in the.non-transducing setting said. impelling means including a revolvahledrive element arranged to engage and drive a portion, of said tape alongsaid guide path at a desired transd'ucing speed when said impellingmeans is. in the transducing setting, said guide means including a coverstructure overlying; the level of said guide path and havingchannel-like opening portions generally corresponding to the guide path,through which said tape may be threaded along said guide path,.portionsv of said cover overlying said core and said backingelement, andalso over lying said drive: element so that opening portions of saidcover structure provide access for placing azportion ofsa'idztapebetween the core face and the. backing face when they are in anon-transducing setting, portions of, the tape placed through openingportionsofisaid: cover along said guide path being arranged to" be.engaged and driven by said drive element when said impelling meansis ina transducing setting;

2. Ina magnetic record transducing. apparatus for transducing magneticrecords on successive elements of a moving tape having a relatively widepermanently magnetizable record surface onone operative side and anopposite side of the same width, the combination comprising: guide meansarranged to guide said tape along an elongated guide path: a magnetic:record transducing head comprising a magnetic core provided with anoutwardly exposed magneticpole core face with said coreextending'substantially entirely along one side of said core face;a'backing element having a backing face for cooperation with said coreface; said core and said backing element being mounted for relativemovement between a non-transducing condition side of thetape into stablemagnetic engagement.

with said core face; said guide meansincluding power-energi'zableimpelling means selectively settable either in a transducing setting inwhich the impelling means impels said tape in a. transducing manner, orin a non-transducable setting in which said impelling means impels saidtape in a non-transducing manner; said impelling means including arevolvabledrive element arranged to selectively operate either in anontransdu'cing condition in which said drive element does" not impelsaid tape or in a transducing condition in which said drive elementimpels said tape in a transducing manner when said impelling means isenergized; and operating means operative in accordance with the settingof said impelling means for causing said magnetic core and said backingelement and also said drive element to be maintained in a transducingconditionwhen saidfiimpelling means is in the transducingsetting, andfor'causing said core and said backing. element and also said driveelement to be maintained in a non-transducing condition when saidimpelling: means is in the non-transducing setting;

3. In: a magnetic record transducing apparatus for transducing magneticrecords on successive elements of a moving tape having a relatively widepermanently magnetizable record surface on one operative side and anopposite side of the same width, the combination comprising: guide meansarranged to guide said tape along an elongated guide path; a magneticrecord trensducing head comprising a magnetic core provided with anoutwardly exposed magnetic-pole core face with said core extendingsubstantially entirely along'one side of said core face; a backing element having a backing face for cooperation with said core face; saidcore and said backing elementbeing mounted for relative movement betweena non-transducingcondition in which said core face is separated fromsaid backing face for receiving therebetween said tape, and atransducing condition in which said core face and said backing face arebiased to contact the opposite sides of one portion of the tape alongsaid guide path for pressing the operative side of the tape into stablemagnetic engagement with said core face; said guide meansincludingpower-energizable impelling means selectively settable eitherin a transducing setting in which the impelling means impels said tapeat a desired low transdu'cing speed in a transducing manner, or at ahigher non-transducing speed in a non-transduc ing setting in which saidimpel'ling means impels said tape in a non-transducing manner; andoperating means operative in accordance with the setting of saidimpelling means for causing said core and said backing element to bemaintained in a transducihg condition when said impelling means is inthetransducing setting, and for causing said core and said backingelement to be maintained in a non-transducible condition when saidimpelli'ng means is in the non-transducing setting said impelling meansincluding a revolvable drive element arranged. to engage and drive aportion of said tape along said guide path at a desired transducingspeed when said impelling means is in the transducing setting, saidguide means including a cover structure overlying the level of saidguide path and having channel-like opening portions generallycorresponding to the guide path, through which said tape may be threadedalong said guide path, portions of said cover overlying said core andsaid backing element, and also overlyingsaid drive element sothat'opening portions of said cover structure provide' access forplacing a portion of said tape between the'core face and the backingface when they are in a non-transducing setting, portions of the tapeplaced through opening portions of said cover along said guide pathbeing arranged to be engaged and driven by said. drive element when saidimpelling means is in a transducing setting.

4. In a magnetic record transducing apparatus for' transdu'cing magneticrecords on successive elements of a moving tape having a relatively widepermanently magnetizable record surface on one operative side and anopposite side of the same width, the combination comprising: guide meansincluding two reels for storing the tape and arranged to. guide saidtape between said reels along an' elongated guide path with the

